Publications

California’s Sacramento–San Joaquin Delta is widely recognized as a highly damaged ecosystem. The Delta is also emblematic of a growing sense worldwide that society needs to do a better job of using scientific knowledge to guide conservation and resource management policies. Fortunately, we now have an unprecedented opportunity to get it right in building structures that support...

Surface water flow controls water velocities, water depths, and residence times, and influences sediment and nutrient transport and other ecological processes in shallow aquatic systems. Flow through wetlands is substantially influenced by drag on vegetation stems but is also affected by microtopography. Our goal was to use microtopography data directly in a widely used wetland model...

Sand Hollow Reservoir in southwestern Utah, USA, is operated for both surface-water storage and managed aquifer recharge via infiltration from surface basin spreading to the underlying Navajo Sandstone. The total volume of estimated recharge from 2002 through 2011 was 131 Mm3., resulting in groundwater levels rising as much as 40 m. Hydraulic and hydrochemical data from the reservoir and...

The temporal variability observed in redox sensitive species in groundwater can be attributed to coupled hydrological, geochemical, and microbial processes. These controlling processes are typically nonstationary, and distributed across various time scales. Therefore, the purpose of this study is to investigate biogeochemical data sets from a municipal landfill site to identify the...

Correlations among observation errors are typically omitted when calculating observation weights for model calibration by inverse methods. We explore the effects of omitting these correlations on estimates of parameters, predictions, and uncertainties. First, we develop a new analytical expression for the difference in parameter variance estimated with and without error correlations for...

Ligands present in dissolved organic matter (DOM) form complexes with inorganic divalent mercury (Hg2+) affecting its bioavailability in pelagic food webs. This investigation addresses the influence of a natural gradient of DOM present in Patagonian lakes on the bioaccumulation of Hg2+ (the prevailing mercury species in the water column of these lakes) by the algae Cryptomonas erosa and...

We investigated the role of land use/land cover and agriculture practices on stream dissolved organic carbon (DOC) dynamics in the Willow Slough watershed (WSW) from 2006 to 2008. The 415 km2watershed in the northern Central Valley, California is covered by 31% of native vegetation and the remaining 69% of agricultural fields (primarily alfalfa, tomatoes, and rice). Stream discharge and...

Numerous adverse effects are associated with the accidental release of ethanol (EtOH) and its persistence in the subsurface. Geophysical techniques may permit non-invasive, real time monitoring of microbial degradation of hydrocarbon. We performed complex resistivity (CR) measurements in conjunction with geochemical data analysis on three microbial-stimulated and two control columns to...

The freshwater zone of the San Antonio segment of the Edwards aquifer is used by residents of San Antonio and numerous other rapidly growing communities in south-central Texas as their primary water supply source. This freshwater zone is bounded to the south and southeast by a saline-water zone with an intermediate zone transitioning from freshwater to saline water (transition zone). As...

Assessments of long-term (multiyear) temporal trends in biological monitoring programs are generally undertaken without an adequate understanding of the temporal variability of biological communities. When the sources and levels of variability are unknown, managers cannot make informed choices in sampling design to achieve monitoring goals in a cost-effective manner. We evaluated...

Groundwater quality in the South Coast Range–Coastal (SCRC) study unit was investigated from May through November 2008 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in the Southern Coast Range hydrologic province and includes parts of Santa Barbara and San Luis Obispo Counties. The GAMA Priority Basin...

Information concerning the availability, use, and quality of water in Assumption Parish, Louisiana, is critical for proper water-supply management. The purpose of this fact sheet is to present information that can be used by water managers, parish residents, and others for management of this vital resource. Information on the availability, past and current use, use trends, and water...